1. Field of the Invention
The present invention relates to a controller of an internal combustion engine which is operable in a compression ignition combustion operation mode in which an air-fuel mixture within a combustion chamber of a cylinder is compressed, and the fuel of the air-fuel mixture is thereby self-ignited and combusted, and a spark ignition combustion operation mode in which the fuel of the air-fuel mixture is ignited and combusted by spark ignition.
2. Description of the Related Art
Conventionally, as can be found in, for example, Japanese Patent Laid-Open Publication No. 2006-97603 (hereinafter referred to as “Patent Document 1”), and Japanese Patent Laid-Open Publication No. 2007-77919 (hereinafter referred to as “Patent Document 2”), an internal combustion engine (hereinafter referred to as “two-ignition-type internal combustion engine”) which is made operable in a compression ignition operation mode (so-called an HCCI-type operation mode) in which the fuel of an air-fuel mixture is self-ignited and combusted by compressing the air-fuel mixture charged into a combustion chamber of a cylinder, and a spark ignition operation mode (so-called SI-type operation mode) in which the fuel of the air-fuel mixture is ignited and combusted by spark ignition is known.
In the techniques seen in Patent Documents 1 and 2, basically, in a case where the rotational frequency and load of the internal combustion engine are in the state of a low-speed and low-load region, the operation of the internal combustion engine in the compression ignition operation mode is performed, and in a case where the rotational frequency and load are in the state of a high-speed and high-load region, the operation of the internal combustion engine in the spark ignition operation mode is performed.
In addition, in the techniques seen in these Patent Documents 1 and 2, a valve mechanism and a supercharger which can separately adjust the opening and closing timing or lift amount of intake valves in the compression ignition operation mode and the spark ignition operation mode is provided, thereby making it possible to properly-perform combustion of an air-fuel mixture in each operation mode.
Additionally, as an internal combustion engine which performs the HCCI-type operation, as seen in, for example, Japanese Patent Laid-Open Publication No. 2000-179368 (hereinafter referred to as “Patent Document 3”), one which is adapted to be able to independently supply two kinds of fuels whose octane values are different from each other to a combustion chamber of a cylinder, thereby adjusting the ratio of the supply amounts of the fuels according to the load of the internal combustion engine, thereby properly performing the combustion of the fuels, is known.
Meanwhile, in the two-ignition-type internal combustion engine, various requirements, such as the air-fuel ratio of an air-fuel mixture which is required to properly operate the internal combustion engine in each operation mode, are different, in addition to the fact that the ignition methods of the fuels in each operation mode are different. For example, although the air-fuel ratio of an air-fuel mixture suitable for the operation in the spark ignition operation mode is an air-fuel ratio near a theoretical air-fuel ratio, the air-fuel ratio of the air-fuel mixture suitable for the operation in the compression ignition operation mode is an air-fuel ratio significantly nearer to lean side than the theoretical air-fuel ratio. For this reason, at the time of the switching of those operation modes, the air-fuel ratio of the air-fuel mixture within the combustion chamber becomes unsuitable even for any operation mode. As a result, troubles are apt to occur such that the combustion of the air-fuel mixture in the combustion chamber becomes unstable, or fluctuations in output torque are caused.
Further, the air-fuel ratio of the air-fuel mixture suitable for the operation in the spark ignition operation mode is an air-fuel ratio nearer to the rich side than the air-fuel ratio of the air-fuel mixture suitable for the operation in the compression ignition operation mode. Therefore, at the time of the switching from the spark ignition operation mode to the compression ignition operation mode, the temperature within the cylinder and the temperature of the wall of the cylinder immediately after the switching, is apt to be a higher temperature than a temperature at the time of continuous operation in the compression ignition operation mode. For this reason, troubles may be caused such that, at the time of the operation of the internal combustion engine immediately after the switching from the spark ignition operation mode to the compression ignition operation mode, the ignition timing of an air-fuel mixture is made earlier than a suitable ignition timing, excessive combustion noises is generated, or knocking occurs.
However, in the control techniques of the two-way ignition internal combustion engine as seen in the above Patent Documents 1 and 2, a control technique which is suitable at the time of the switching of the operation mode is not provided. Thus, there is a possibility that troubles may be caused as described above. Further, since a drive mechanism of complicated intake valves is required in the techniques seen in Patent Documents 1 and 2, the configuration of the internal combustion engine is complicated, and the optimal control of the air-fuel ratio of an air-fuel mixture, etc. is difficult due to the delay of the operation of the drive mechanism of the intake valves, etc.